In -Oath to Nyx- It says it requires Full moon drawn with Nyx's blessing on an altar cover...What is that and how do I get it for the ritual? It also calls for blessing oil but does not say how/when to use it?

That's always a problem in using a ritual written by someone else where the directions aren't clear. Normally I would suggest asking the person who wrote the ritual to clarify it, but their account seems to have been deleted.

What I would recommend, rather than trying to do the ritual exactly as it is written is to create a ritual of your own using the one you have from SOM as an inspiration. After all, if you are pledging yourself to the service of Nyx what could be better than doing something particularly meaningful to you and using your own words and symbols.

Some of the things suggested in that posted ritual have no connection to the Gods of Egypt, like sweetgrass for instance which is from the New World. Better choices for incense and purification would be frankincense, myrrh, and sandalwood. And water is always an appropriate offering to the Gods of the desert land.

If you want to use the blessing oil, I would suggest using that to annoint your candles before lighting them.